The term signalling generally refers to transmitting, from one telecommunication device to another, some information that relates more to the management of the communication connection than directly to the payload, like speech or data, for the transmission of which the communication connection between the devices has been established. For example in mobile telephony signalling is used to exchange measurement results, announcements, commands and short messages between a mobile terminal and a base station, or between the different devices belonging to the fixed parts of the mobile telephone network.
User-to-User Signalling or UUS is a procedure recently disclosed as a supplementary service in some advanced telephone systems. Its inteded use is the transmission of a limited amount of subscriber generated information (UUI; User-to-User Information) to and/or from another user in association with a call between the users concerned. The nature of UUS dictates that the network that mediates the communication between the users does not interpret the UUI or act upon it in any way, i.e. it is passed “transparently” through the network. This patent application will refer to the known aspects of UUS in the form in which they have been disclosed in the document “GSM 02.87: GSM Digital Cellular Telecommunications System (Phase 2+); User-to-User Signalling (UUS); Service Description, Stage 1, v.5.2.1”, which has been published by ETSI (European Telecommunications Standards Institute) in November 1997 and which is incorporated herein by reference. However, the invention is applicable in association with all current and future telecommunication systems which support user-to-user signalling in a form comparable to that described below.
There are, at the time of filing this patent application, three subclasses of UUS, namely Service 1, Service 2 and Service 3. A user has access to these services as described in his/her subscription contract with the system operator. According to Service 1, UUI can be sent and received during call setup and termination by embedding UUI into the appropriate call control messages. Service 1 can be an implicit part of each call setup, whereby the user does not have to initiate the transmission of a UUS message separately, or it may be explicit in which case the user has to initiate an appropriate procedure. Service 2 encompasses the UUS messages that are sent and received after the calling party has received an indication that the called party has been informed of the call, but before the call is actually established. The network is not responsible for delivering a sent Service 2 message to its recipient before the call will be established. All such UUS messages that are sent and received during an established call connection belong to Service 3.
For example an ISDN system (Integrated Services Digital Network) allows as a network option the transfer of UUI with a maximum length of 32 octets for Service 1. The endpoints of a point-to-point connection where UUS is used may be mobile-to-mobile, mobile-to-PLMN (Public Land Mobile Network), mobile-to-ISDN network, mobile-to-ISDN terminal, or mobile-to-PSTN (Public Switched Telephone Network). If the other end is PLMN, ISDN network or ISDN terminal, it must be equipped with sufficient ISUP (ISDN Signalling User Part) signalling support known as such to the person skilled in the art. If the other end is PSTN, it must be equipped with sufficient inter-exchange ISUP signaling support known as such to the person skilled in the art.
The prior art publications disclose only a very limited number of actual applications for UUS. It is therefore an object of the invention to present a method and the necessary equipment for providing added value to a telephone connection by using specific applications of UUS.